Objective To analyze the etiological characteristics of two strains of Escherichia albertii first identified in Baoshan District, Shanghai, in 2024, to explore their antibiotic resistance characteristics, virulence characteristics, and multilocus sequence typing (MLST) to elucidate their genetic evolutionary relationships, so as to provide a scientific basis for the surveillance and control of Escherichia albertii in the local area.

Methods A total of 457 anal swabs were collected from patients with diarrhea in 2024, from which two suspected Escherichia albertii strains were isolated. The isolated strains were identified through mass spectrograph analysis, biochemical identification, and polymerase chain reaction (PCR) test. Microdilution broth method was used for the antimicrobial susceptibility testing, and whole-genome sequencing was performed for molecular characteristic analysis.

Results Mass spectrograph analysis and PCR test initially identified the two strains as Escherichia coli (E. coli), but their biochemical profiles were inconsistent with those of E. coli. Genomic sequencing identified the strains as Escherichia albertii, and which were named as S1 and S2, respectively. The antimicrobial susceptibility test showed that both strains were susceptible to β‑lactam antibiotics and moderately susceptible to polypeptide antibiotics. S1 was resistant to chloramphenicol (CHL), streptomycin (STR), tetracyclin (TET), florfenicol (FFC) and nalidixic acid (NAL), and carried five resistance genes including APH（6）， APH（3）， gyrA， tet andflor, whereas S2 was susceptible to the five antibiotics mentioned above. Neither of the two strains contained the stx virulence gene, but S2 harbored the astA virulence gene. The two Escherichia albertii strains had the MLST types of ST4638 and ST4606, respectively. The genome size of the two strains was 4.5 Mb, and the closest relative strain was GTC14781 (Escherichia albertii). The average nucleotide identity (ANI) values to the reference genome of E. coli were both below 90%. S1 did not have the H serotype defined in the current database. S1 and S2 differed by 28 267 single-nucleotide polymorphisms (SNPs), and no homologous strains were found in comparison with the data in the GeneBank database.

Conclusion Two strains of Escherichia albertii are initially identified in Baoshan District of Shanghai. Strain S1 shows strong multidrug resistance, while strain S2 carries diarrheagenic virulence genes. The two strains have a distant genetic relationship and exhibits a pattern of sporadic occurrence. It is recommended to utilize whole-genome sequencing technology to enhance the epidemiological surveillance and laboratory detection of Escherichia albertii.